Approximately 10% of cases of amyotrophic lateral sclerosis (ALS) are familial (FALS), and 20% of these cases are caused by mutations in an enzyme called superoxide dismutase type 1 (SOD1). Several lines of evidence have made it clear that the reason for motor neuron death in FALS is not due to a deficiency in enzymatic activity by the mutated SOD1 protein, but due to toxicity of the mutant (MT) enzyme. One attractive hypothesis is that the mutations in the SOD1 protein cause it to misfold, and the misfolding leads to aggregation of SOD1 within the cell and an associated interference with normal protein-protein interactions important for cell survival. Relevant to this proposal is the recent demonstration that monoclonal antibodies that are MTSOD1-specific can be therapeutically effective in a MTSOD1 transgenic mouse model of FALS. It may be that single chain fragments of variable region (scFvs) of antibodies directed against MTSOD1 can complement anti-MTSOD1 monoclonal antibodies since scFvs provide the opportunity for expression intracellularly (as intrabodies). We have isolated a number of scFvs of antibodies directed against SOD1, including an scFv that is directed against A4V MTSOD1 - the most common mutation of SOD1 seen in North America, and one that usually causes death in less than a year. We now plan to: prepare additional scFvs against wild type and MTSOD1;test whether scFvs delivered by means of transfection or virus vector delivery decrease aggregate formation and/or toxicity of MTSOD1 expression in a MN cell line and primary MNs;test whether scFvs delivered by means of a replication-deficient recombinant adeno-associated virus (AAV) into FALS transgenic mice decrease MTSOD1 aggregation, delay the onset or slow the progression of disease These studies may clarify the reasons for cell death as well as identify possible therapeutic approaches for FALS patients with SOD1 mutations. The knowledge of the mechanisms responsible for motor neuron death in FALS and its treatment may guide us in our understanding of non-inherited ALS - especially since recent information suggests that biochemical changes in SOD1 may contribute to disease in non-inherited ALS. PUBLIC HEALTH RELEVANCE: Amyotrophic lateral sclerosis (ALS) is a desperate disease in which there is no cure or effective treatment. This proposal involves raising antibodies directed against a protein that is mutated in some cases of familial ALS and has been implicated in the development of sporadic ALS. The antibodies that we raise may help understand the cause of ALS and potentially provide a direction for treatment of inherited ALS as well as sporadic ALS.